Fuel injection apparatus for spark plug-ignited internal combustion engines

ABSTRACT

In a fuel injection apparatus the air-fuel ratio is controlled by an air sensor which is deflected against a return force by the intake air and which, as a function of the extent of its deflection, controls the output of a fuel metering valve. To ensure a leaner fuel mixture subsequent to a cold engine start, there is provided a first temperature-dependent control element which is responsive to the water coolant temperature and, upon the increase of the latter, causes an increase in the bias of a spring augmenting, in turn, said return force to bring about a leaner fuel mixture and a second temperature-dependent control element which is responsive to a separate heater means and which, for a very short period subsequent to the starting of the cold engine, hinders said first temperature-dependent control element to increase said bias.

United States Patent [191 Knapp [54] FUEL INJECTION APPARATUS FOR SPARKPLUG-IGNITED INTERNAL COMBUSTION ENGINES [75] Inventor: Heinrich Knapp,725 Leonberg-silberberg, Germany [73] Assignee: Robert Bosch GmbH,Stuttgart, Germany 22 Filed: Dec. 28, 1971 21 Appl. No.: 212,955

[30] Foreign Application Priority Data 56] References Cited UNITEDsTATEsi ATEN'Ts Eckert et al. ..l23/l 19 R [451 May 1,1973

Primary Examiner-Wendell E. Burns Att0rneyEdwin E. Greigg [5 7] ABSTRACTIn a fuel injection apparatus the air-fuel ratio is controlled by an airsensor which is deflected against a return force by the intake air andwhich, as a function of the extent of its deflection, controls theoutput of a fuel metering valve. To ensure a leaner fuel mixturesubsequent to a cold engine start, there is provided a firsttemperature-dependent control element which is responsive to the watercoolant temperature and, upon the increase of the latter, causes anincrease in the bias of a spring augmenting, in turn, said return forceto bring about a leaner fuel mixture and a second temperature-dependentcontrol element which is responsive to a separate heater means andwhich, for a very short period subsequent to the starting of the coldengine, hinders said first temperature-dependent control element toincrease said bias.

5 Claims, 2 Drawing Figures Patented May 1, 1973 I 3,730,155

2 Sheets-Sheet 1 Patented May 1, 1973 2 Sheets-Sheet 2 kc/cm Fig.2

FUEL INJECTION APPARATUS FOR SPARK PLUG- .IGNITEI) INTERNAL COMBUSTIONENGINES BACKGROUND OF THE INVENTION This invention relates to a fuelinjection apparatus associated with a spark plug-ignited internalcombustion engine which operates on fuel continuously injected into theair intake tube. In the latter there are serially arranged an air sensorand an arbitrarily operable butterfly valve. Theair sensor isdisplaceable by the air flow against a constant return force to anextent proportionate to the throughgoing air quantities. The air sensordisplaces the fuel rack of a fuel quantity distributor valve disposed inthe fuel line for the metering of fuel quantities in proportion to thethroughgoingair quantities. The aforenoted return force is derived fromthe pressure of a liquid which is supplied continuously and underconstant pressure through a pressure conduit and which affects a controlplunger operatively connected to the air sensor. The pressure of saidliquid is variable by a pressure control valve which is, in turn,responsive to at least one engine variable. Besides the pressure controlvalve there is provided a temperatureresponsive control elementoperating a closing member disposed in a bypass channel whichcircumvents the butterfly valve. Said bypass is closed after the normaloperational temperatures of the internal combustion engine are reached.

In a fuel injection apparatus of the aforenoted type the difficulty isencountered that the enriching of the fuel-air mixture for the warm-upoperation has to be substantially greater immediately after starting theengine than it is necessary for the subsequent engine run after acertain period. Thus, assuming for example an engine start at 20 C, thefuel mixture, by the time the engine runs at C of coolant watertemperature, is enriched approximately twice the extent necessary tokeep the engine running immediately after starting and to ensureoptimally clean exhaust gases at 0 C of coolant water temperature. Thereason is the increase in fuel condensation at the cold cylinder wallswhich are pre-warmed by virtue of the several ignitions, whereas thecoolant temperature still remains practically the same. An apparatus ofthe aforenoted type isdescribed inPublished German Application (DOS)1,960,144.

I OBJECT AND SUMMARY OF THE INVENTION It is an object of the inventionto provide an improved fuel injection apparatus wherein the fuelenriching for the warm-up run is improved in such a manner that for avery short period immediately subsequent to the starting of the-engine,there is effected the usual fuel enriching whereupon, in atemperaturedependent manner, the extent of the enriching is graduallydecreased to assume a value which ensures an optimal exhaust gascomposition.

Briefly stated,.according to the invention, in addition to theaforenoted temperature-responsive control element which is disposed insaid bypass and which varies the bias ofa spring associated with saidpressure control valve, there is provided an additional, secondtemperature-dependent control element which, during and for ashortperiod immediately subsequent to the starting of the engine, exertsa force opposing that of said spring.

The invention will be better understood, as well as further objects andadvantages become more apparent, from the ensuing detailed specificationof a preferred, although exemplary, embodiment taken in conjunction withthe drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal, in partschematic, sectional view of a fuel injection apparatus according to theinvention and FIG. 2 is a diagram illustrating the control pressure ofthe pressurized liquidas a function of temperature.

DESCRIPTION OF THE EMBODIMENT Turning now to FIG. 1, there is shown afuel injection apparatus in which the intake air flows from an airfilter l to one ormore engine cylinders (not shown) through an airintake tube which comprises a portion 3 in which there is disposed anair sensor 4, a hose connection 5 and an intake tube portion 6 in whichthere is arranged an arbitrarily operable butterfly valve 7. The airsensor 4 is formed as a disc which is oriented normal to the directionof air flow and which is movable in the intake tube portion 3 as asubstantially linear function of the air quantities flowing through theair intake tube. In case of a constant return force applied to the airsensor 4, as well as a constant air pressure prevailing upstream of theair sensor 4, the pressure between the air sensor 4 and the butterflyvalve 7 remains substantially constant. The air sensor 4 directlycontrols a metering and fuel distributor valve 8. The motion of the airsensor 4 is transmitted to the control plunger 12 of the fuel meteringvalve 8 by means of a nose portion 11 of a lever 10 which is affixed tothe air sensor plate 4 and which is pivotable with low friction about ashaft 9. The radial terminal face 13 of the control plunger 12 isexposed to pressurized liquid which serves as the return force for theair sensor 4.

The supply of fuel is effected by a fuel pump 16 which is driven by anelectromotor 17 and which draws fuel from a fuel tank 36 forcing itthrough a conduit 18 to the fuel metering valve 8. From the conduit 18the fuel is admitted to a channel 19 disposed in a housing of thefuelmetering valve 8. The channel 19 merges into an annular groove 20from which there extend ports 21 to a cylinder 22 in which the controlplunger 12 is reciprocably disposed. In the latter there is provided, byvirtue of two spaced lands, an annular circumferential groove 23 whichis in continuous communication with the ports 21. Dependent upon theposition of the control plunger 12 the annular groove 23 overlaps to agreater or lesser extent control slots 24 through which the fuel mayflow from the annular groove .23 into channels 25 which, in turn, leadto the individual fuel injection valves (not shown) disposed in the airintake tube of the internal combustion engine. One part of the fuelflows from the annular groove 20 into a channel 26 and is admitted to anannular groove 27 wherefrom it flows through ports 28 into a conduit 29.The latter is in communication through a damping throttle 30 with thepressure chamber 31 (forming part of the cylinder 22) in which there isdisposed the radial work face 13 of the control plunger 12.

Through the conduit 29 the fuel serving as pressurized liquid isadmitted to a first pressure control valve 32 which is formed as a flatseat valve including a diaphragm 33 and a stationary valve seat 34. Thefuel flowing through the control valve 32 is returned in a depressurizedcondition into the fuel tank 36 through a return conduit 35. Thediaphragm 33 is loaded by a spring 37, the bias of which is changed as afunction of operational variables of the internal combustion engine. Forthis purpose there is provided a three-dimensional cam 38 which isrotatable as a unit with the arbitrarily adjustable butterfly valve 7and which may be axially displaced as a function of the vacuumprevailing downstream of the butterfly valve 7 in the suction tube. Thethree-dimensional cam 38 is axially slidably held on the shaft 39 whichis integral with the butterfly valve 7. The rotary motion of the shaft39 is transmitted by means of a pin 40 to the three-dimensional cam 38which, at one frontal face, is rotatably secured to a diaphragm 41bounding a vacuum chamber 42. The latter is in communication by means ofa conduit 43 with the air intake tube at a location downstream of thebutterfly valve 7. If the vacuum is of a sufiiciently large value, thethree-dimensional cam 38 is axially displaced by the diaphragm 41against the force of a return spring 44 disposed in the vacuum chamber42. A follower pin 45 scans the surface of the three-dimensional cam 38and through a spring seat disc 46, controls the bias of the spring 37 toaffect the pressure of the pressurized liquid serving as the resettingforce for the air sensor 4.

From the conduit 29 there extends a conduit 50 which is connected to asecond pressure control valve 53 from which there extends a returnconduit 55 to the fuel tank 36. The pressure of the pressurized liquidserving as a return force for the air sensor 4 may be controlled as afunction of temperature by means of the second pressure control valve53. The latter is formed as a flat seat valve having a stationary valveseat 57 and a diaphragm 58 which is loaded by a spring 59 in the closingdirection of the valve 53.

The chamber 60 accommodating the spring 59 forms one part of a bypassconduit 61, 62 circumventing the butterfly valve 7 in the suction tube.For the sake of clarity the bypass conduit itself is not shown in FIG.1, only its connections with the suction tube portion 6 and with thepressure control valve 53 are indicated. In chamber 60 there is disposeda plunger piston 64 which controls the flow passage section of thebypass conduit 61, 62 and which also serves as a spring seat disc forthe spring 59.

The displacement of the piston plunger 64 is effected by a firsttemperature-dependent control element (heat expandable regulator) 63which, when the internal combustion engine is cold, compresses thespring 59 to a lesser extent and opens the bypass 61, 62 to a greaterextent than in case of a warm engine. In this manner, under cold engineconditions more pressurized liquid flows through the valve 57, 58 andthus the pressure of the fuel working as a return force is smaller.Consequently, the injected fuelquantities are relatively increased withrespect to the air quantities to obtain a richer mixture.

That terminus of the spring 59 which is remote from the control plunger64 engages a spring seat disc 65 which exerts a force on the diaphragm58 through an intermediate member 66. The spring seat disc 65 has at itsside remote from the spring 59 an opening 67 into which there extendsone end of a bimetal spring 68. The other end of the latter issurrounded by a heater element 69 which, together with the bimetallicspring 68, forms a second temperature-dependent control element 68, 69.In the shown position, prior to the operation of the internal combustionengine, a rivet 70 attached to the bimetal spring 68 is in engagementwith the spring seat disc 65.

OPERATION OF THE FUEL INJECTION APPARATUS When the internal combustionengine is running, the pump 16 driven by the electromotor 17, draws fuelfrom the fuel tank 36 and forces the same through the conduit 18 to thefuel metering valve 8. Simultaneously, the engine draws air through theair intake tube 3, 5, 6, as a result of which the air sensor 4 isdeflected in a clockwise direction (as viewed in FIG. 1) from itsposition of rest.

In response to the deflection of the air sensor 4 the lever 10, with itsintegral nose 11, displaces the control plunger 12 to the left, thusopening the control slots 24 to a greater extent. Thus, the fuelquantity passing through the metering slots 24 and admitted to the fuelinjection valves (not shown) corresponds to the setting magnitude of theair sensor 4. From the annular groove 23 of the control plunger 12, onepart of the fuel is admitted through the channel 26 into the pressurechamber 31 where it affects the frontal radial face 13 of the controlplunger 12. Other parts of the fuel flow from the channel 26 through theconduit 29 to the first pressure control valve 32 and through a conduit50 to the second pressure control valve 53.

The direct coupling of the air sensor 4 with the control plunger 12results in a constant ratio between the air quantities and the fuelquantities insofar as the' The measuring magnitudes for load and rpm ofan internal combustion engine are the angular position of the butterflyvalve and the vacuum in the air intake tube. Consequently, the returnforce is expediently varied as a function of these two magnitudes. Suchvariation is brought about by the change in the bias of the spring 37 ofthe pressure control valve 32 by shifting the spring seat disc 46. Thelatter shift, in turn, is effected by the rotary and axial motions ofthe threedimensional cam 38 executed, respectively, in response to theangular position of the butterfly valve 7 and the pressure in thesuction tube. If for example, in a full load condition the butterflyvalve 7 is in a position in which the suction tube is fully open, then ahighest output, that is, a relatively rich air-fuel mixture is desired.Since the bias of the spring 37 of the first pressure control valve 32determines the pressure of the fuel which affects the radial face 13 ofthe control plunger 12, the return force affecting the air sensor 4 hasto be somewhat reduced to permit the control plunger 12 to be shiftedinto a position in which the control slots 24 are opened to a greaterextent and, accordingly, larger fuel quantities can be injected.Conversely, under partial load conditions, by virtue of a relativelyhigher pressure exerted on the radial face 13 of the control plunger 12,there is obtained a relatively smaller deflection of the air sensor 4and, as a result, the air-fuel mixture will be leaner.

When the vehicle with which the internal combustion engine is associatedcoasts in gear, the threedimensional cam 38, because of the substantialvacuum in the air intake tube, is displaced against the force of thespring 44 so that the spring 37 of the first pressure control valve 32will be biased to a greater extent. In this manner the return forceexerted on the air sensor 4 is increased so that despite the slight airleakage quantities that may flow through the closed butterfly valve 7,there will be no deflection of the air sensor 4 and thus no fuelquantities will be injected.

If first the effect of the second temperature-dependent controlelement68, 69 is disregarded, in case of a cold engine there is obtained anenriching of the airfuel ratio, since the heat-expandable regulator 63of the second pressure control valve 53 causes the pressure of the fuelserving as a return force to be decreased in the chamber 31. In thisoperational condition the plunger piston 64 displaced by theheat-expandable regulator 63 maintains the bypass conduit 61, 62 open.In this manner, the greater engine friction at the cold start of theengine is compensated by a correspondingly higher mixture flow rate.

The first temperature-dependent control element 63 which responds to thecoolant water temperature, effects a leaner fuel mixture (by compressingthe spring 59 and thus increasing the fuel pressure at the radial workface 13 of the control plunger 12) only with a substantial delay. Since,however, already a few moments following the starting of the engine thecylinder walls, because of the preceding ignitions, have been prewarmedand thus a fuel condensation caused by the previously cold cylinderwalls occurs to a decreasing degree, it is expedient to simultaneouslyreduce the enrichment of the air-fuel mixture to such an extent that aclean run of the engine is ensured. According to the invention, such adecrease in the fuel enriching is ensured by causing the secondtemperature-dependent control element 68, 69 to work against the spring59 for a short period immediately after, starting of the internalcombustion engine. The heater 69 is energized by, eg closing itselectrical circuit simultaneously with turning on the engine ignition.

Turning now to FIG. 2 there is shown the fuel pressure exerted on thecontrol plunger 12 as a function of the coolant water temperature ascontrolled by the second pressure control valve 53. In a device for thewarm-up run of the engine without the second temperature-dependentcontrol element 68, 69, the spring 59 should be designed according tothe pressure characteristic curve a. According to the invention,however, the spring 59 is designed to correspond to the pressurecharacteristic curve b. The cold bimetal spring 68 works against thespring 59 at the moment of starting in such a manner that the curve a isobtained for the engine run after starting. The heat output of theheater element 69 is determined in advance in such a manner that,dependent upon the starting temperature, the bimetal spring 68 is, aftera correspondingly short time, bent away from the spring seat disc 65.Consequently, after this occurrence the spring seat disc 65 and thus thediaphragm 58 are loaded only by the spring 59. The transition from thecurve a to the curve b occurs, dependent upon the temperature at thestarting, along one of the curves c. At normal operating temperatures ofthe coolant water, the spring 59 remains biased to a constant extentaccording to the curve d.

That which is claimed is: i

1. In a fuel injection apparatus serving a spark plugignited internalcombustion engine operating on fuel continuously injected into the airintake tube thereof, said apparatus being of the type that has (a) anarbitrarily operable butterfly valve disposed in said air intake tube,(b) an air sensor disposed in said air intake tube spaced from saidbutterfly valve, said air sensor being displaceable by and as a functionof the air quantities passing through said air intake tube, (0) a fuelquantity distributor valve for metering the fuel quantities to beinjected, (d) means connecting said air sensor with said fuel quantitydistributor valve to effect metering of said fuel as a function of thedeflection of said air sensor, (e) means supplying a return forceaffecting said air sensor in opposition to the force exerted thereon bythe flow of intake air, said means supplying said return force includesa control plunger operatively connected to said air sensor and cylindermeans accommodating said control plunger and containing liquid underpressure exerting said return force on said control plunger, theimprovement comprising A. a pressure control valve hydraulicallyconnected to said cylinder means for varying the pressure of said liquidin said cylinder means, said pressure control valve including a springthe bias of which affecting said pressure in said cylinder means,

B. a first temperature-responsive control element sensing the enginetemperature and causing an increase in the bias of said spring as theengine temperature increases,

C. a second temperature-responsive control element opposing, whenunheated, the operation of said first temperature-responsive controlelement, and

D. a separate heater means operatively coupled to said secondtemperature-responsive control element for heating the same causingdiscontinuance of its opposing effect on said firsttemperatureresponsive control element.

2. An improvement as defined in claim 1, including means to energizesaid separate heater means immediately after starting said engine.

3. An improvement as defined in claim 1, said secondtemperature-responsive control element being formed as a bimetal springbeing in engagement, when unheated, with said first-named spring andbending away therefrom when heated.

4. An improvement as defined in claim 1, said pressure control valvebeing hydraulically connected to said cylinder means downstream thereof.

5. An improvement as defined in claim 1, including A. a bypass channelcircumventing said butterfly valve and B. means connected to said springfor varying the flow passage section of said bypass channelsimultaneously with the variation of the bias of said spring.

1. In a fuel injection apparatus serving a spark plug-ignited internalcombustion engine operating on fuel continuously injected into the airintake tube thereof, said apparatus being of the type that has (a) anarbitrarily operable butterfly valve disposed in said air intake tube,(b) an air sensor disposed in said air intake tube spaced from saidbutterfly valve, said air sensor being displaceable by and as a functionof the air quantities passing through said air intake tube, (c) a fuelquantity distributor valve for metering the fuel quantities to beinjected, (d) means connecting said air sensor with said fuel quantitydistributor valve to effect metering of said fuel as a function of thedeflection of said air sensor, (e) means supplying a return forceaffecting said air sensor in opposition to the force exerted thereon bythe flow of intake air, said means supplying said return force includesa control plunger operatively connected to said air sensor and cylindermeans accommodating said control plunger and containing liquid underpressure exerting said return force on said control plunger, theimprovement comprising A. a pressure control valve hydraulicallyconnected to said cylinder means for varying the pressure of said liquidin said cylinder means, said pressure control valve including a springthe bias of which affecting said pressure in said cylinder means, B. afirst temperature-responsive control element sensing the enginetemperature and causing an increase in the bias of said spring as theengine temperature increases, C. a second temperature-responsive controlelement opposing, when unheated, the operation of said firsttemperatureresponsive control element, and D. a separate heater meansoperatively coupled to said second temperature-responsive controlelement for heating the same causing discontinuance of its opposingeffect on said first temperature-responsive control element.
 2. Animprovement as defined in claim 1, including means to energize saidseparate heater means immediately after starting said engine.
 3. Animprovement as defined in claim 1, said second temperature-responsivecontrol element being formed as a bimetal spring being in engagement,when unheated, with said first-named spring and bending away therefromwhen heated.
 4. An improvement as defined in claim 1, said pressurecontrol valve being hydraulically connected to said cylinder meansdownstream thereof.
 5. An improvement as defined in claim 1, includingA. a bypass channel circumventing said butterfly valve and B. meansconnected to said spring for varying the flow passage section of saidbypass channel simultaneously with the variation of the bias of saidspring.